If you don't have white boards available, you can also print the attached DNA pieces on cardstock, have your students cut them out and glue them on paper. The simulation of the replication process won't work very well though....

Grouping:

Students will work in pairs.

Setting:

Regular classroom

Time needed:

About 30 minutes intro presentation

About 20 minutes for the magnetic whiteboard activities (if you do the activity using the paper pieces, this part will take much longer)

5 minute debrief

Author Name(s):

SEP staff

Summary:

Students assemble a DNA molecule, using magnetic pieces representing sugar, phosphate and the nitrogenous bases on magnetic whiteboards. Students then model the process of semi-conservative DNA replication applying the complementary base pairing rule.

Prerequisites for students:

Students should be familiar with the process of cell division (mitosis) and understand that DNA replication has to occur prior to cell division in order to ensure that both daughter cells will receive a complete set of the genetic information.

Learning goals/objectives for students:

Students will be able to name the building blocks that make up DNA.

Students will be able to describe the basic structure of the DNA molecule.

Students will be able to model the process of DNA replication.

Content background for instructor:

DNA(deoxyribose nucleic acid) is a macro-molecule that consists of repeating units, called nucleotides. Nucleotides are made up of a sugar molecule, a phosphate and one out of four nitrogenous bases (Adenine, Thymine, Guanine, Cytosine). DNA is always found as double chains of nucleotides forming a structure that resembles that of a twisted ladder. Repeating sugar and phosphate molecules are forming the sides or backbone of the ladder and pairs of bases the rungs of the ladder. Adenine always pairs with Thymine and Guanine always pairs with Cytosine (A-T, C-G); they are complimentary base pairs. Consequently there are always as many "A's" than there are "T's" in a DNA molecule and equal numbers of "C's" and "G's" (Chargoff rule).

DNA carries the genetic information of the cell. When cells divide, they have to copy that genetic information and pass on one copy to each daughter cell. DNA replication is "semi-conservative": The DNA double helix unravels and unzips (the weak hydrogen bonds between the bases are broken by an enzyme (helicase). Each original DNA strand now serves as a template for the new. Free-floating nucleotides, that are made in other parts of the cell, match with their complimentary nucleotide "partner" and link up. In this way, a single DNA molecules becomes two. One strand of each of the two DNA molecules is the original (conserved), and one strand is freshly assembled (hence: Semi (half) conservative replication).

Funded in part by by the National Center for Research Resources and the Office of Research Infrastructure Programs (ORIP) of the National Institutes of Health through Grant Number R25 OD011097 and by an undergraduate science education award from the Howard Hughes Medical Institute